Coded track circuit railway signaling system



c. E. STAPLES 2,692,940

CODED TRACK CIRCUIT' RAILWAY SIGNALING SYSTEM 7 3 Sheets-Sheet l E W 72i6 S m ifi R. w Q w; h &m w k m m @T' 5 \QNW .NQNNQ W m W a E 1 ilimiillLu .M u i Q TN m m u .M &

uypm.

HIS ATTORNEY m k m y m 6 wu m x1 @JFQ m m a Oct. 26, 1954 Filed Feb. 11,1955 q w sw m i 1 E R M 2% mg Patented Oct. 26, 1954 UNITED STATES ATENTOFFICE CODED TRACK CIRCUIT RAILWAY SIGNALING SYSTEM Application February11, 1953, Serial No. 336,225

3 Claims. (Cl. 246--33) My invention relates to an automatic blocksignaling system of the coded type for single track railroads.

An object of my invention is to provide an improved system of the typedescribed which can be installed and maintained at a minimum cost sothat the system is available for use in track stretches where the numberof trains operated is not sufficient to warrant installation of a morecomplete system.

Another object of my invention is to provide an improved system of thetype described which is arranged so that the system is controlledentirely over the track rails in the single track stretches to therebyreduce the amount of line wire to be used.

A further object of my invention is to provide an improved system of thetype described in which each of the track sections in a single trackstretch is provided with two track circuits employing coded energy, onefor each direction of trafiic.

According to my invention 1 provide in a stretch of single track railwaybetween two passing sidings, a station leaving and a station enteringsignal adjacent each passing siding and intermediate signals controllingtrain movements through the stretch. At each signal location, a pair ofinsulated joints is provided so that the stretch is divided into two endsections adjacent the passing sidings and an intermediate sectionbetween the two end sections. Each of the end track sections is providedwith two track circuits, one for each direction of traffic, and each ofthese track circuits is provided with code transmitting means atopposite ends of the sections and track relay means at the end of thesection opposite to the code transmitting means associated therewith.The track circuits from the passing sidings to the intermediate signalsare of the polar coded type and the track relay means in these trackcircuits are selectively responsive to currents of opposite polarity. Inthis manner, the intermediat signals associated with their trackcircuits are provided with a third indication.

In the intermediate section, each end is provided with apparatusincluding code generating means, code halving means and codetransmitting means. In addition, a code following track relay isprovided at each end, responsive to the code being transmitted from theother end. Furthermore, at one end of the intermediate section, areverse code generating means is also provided. Means is provided forconnecting the code generating and halving means at the one end of theintermediate section to their associated code transmitting means when atrain occupies the end section adjacent the other end of theintermediate section or when a train occupies the intermediate section.Means is provided for connecting the code generating and halving meansat the other end of the section to their associated code transmittingmeans except When the adjacent end section is occupied. Means is furtherprovided for connecting the reverse code generating means to itsassociated code transmitting means when the entire stretch is vacant.

The track relay means at each end of each section controls the signalassociated therewith.

Other objects of my invention will appear hereinafter as thecharacteristic features of construction and mode of operation of myinvention are described in detail.

I shall describe one form of apparatus embodying my invention and shallthen point out the novel features thereof in claims.

In the accompanying drawings, Figs. la and lb when placed side by sidein the named order, with Fig. 1a at the left, form a diagrammatic viewshowing one circuit arrangement embodying my invention.

Figs. 2a through 2 are diagrammatic views of stretch of track controlledby a system embodying my invention showing the cod assignments andsignal aspects as an eastbound train moves through the stretch of track.

Figs. 3a through 3f are diagrammatic views of a stretch of trackcontrolled by a system embodying my invention showing the codeassignments and signal aspects as a westbound train moves through thestretch of track.

Similar reference characters refer to similar parts in each of theseveral drawings.

Referring now to the Figs. 1a and 1b, there is shown a stretch of singletrack railway made up of track rails l and 2. Adjoining the Western endof the stretch is a western passing siding W; adjoining the eastern endof the stretch is an eastern passing siding E. The stretch of singletrack is divided into track sections 2-3T, 4-5T and 6'iT by insulatedjoints 3 placed in the rails. At the western passing siding W, there isprovided a station entering signal S and a station leaving signal 2S.Each of the signals governing traffic movement into and through thestretch may be of any suitable type, and are here shown as the wellknown color light type of signal. The control circuits for signal ISform no part of my invention and are omitted. Signal 28 is controlled bya relay ZDR which in turn is supplied energy from a decoding unit IBDDU.The decoding unit ISIJDU is of a design well known in the art of railwaysignaling and will supply sufficient energy to relay 2DR to cause it topick up when and only when the decoding unit is supplied with energycoded at a 180 code rate. The decoding unit is in turn controlled by atrack relay ZTR through a decoding transformer ZTT. A reverse codetransmitting relay ZRCR controls the supply of energy from a trackbattery 2TB to the track section 2-3T. The polarity of the energysupplied to section 2-3T is controlled by a relay IDP which is in turncontrolled jointly by the relay ZDR and a relay IGP. The circuitcontrolling relay IGP forms no part of my invention and it will sufficeto say that relay IGP will be energized when signal I S indicates otherthan stop.

At the intermediate signal location A, two track relays 3DTR and 3HTRare at times connected in series across the rails of section 2-3T. Thesetrack relays are of the biased type, having contacts which are picked upwhen and only when current flows through the relay winding in thedirection indicated by the arrow thereon. As can be seen in the Fig. 1a,relays 3DTR and 3HTR are responsive to currents of opposite polarity.Relay lDTR controls a front contact repeater relay SDTFP and relay BHTRcontrols a front contact repeater relay 3HTFP. These four relays jointlycontrol a signal control relay SHR which, in turn, controls a signal 33in conjunction with relay SDTFP.

Two coders 150T and IEOCT are also provided at location A. These codersmay be of any of the several types well known in the art of railwaysignaling and are arranged so that coder 750T will continuously operateits contacts at a 75 code rate while coder I80CT will continuouslyoperate its contacts at a 180 code rate. A magnetic stick relay 4BCR isalso provided at the intermediate signal location A. This type of relayis well known in the art and has the characteristic of operating itscontacts in accordance with the direction of the flow of current throughits winding and holding its contacts in the position to which they werelast energized. As shown and described, a magnetic stick relay willoperate its contacts in a direction opposite to the direction of currentflow through its winding.

Furthermore, at intermediate signal location A, a biased track relay ITRassociated with the track section 4-5T, is also provided. A frontcontact repeater relay 4TB? is controlled by relay lTR and these tworelays jointly control a signal control relay IHR. Relay 4HR in turncontrols a signal 43. Furthermore, in conjunction with several otherrelays, relay 4HR controls the code rate at which a code transmittingrelay 3CTP codes energy supplied from a battery 3TB to the track section2-3T. Another code transmitting relay 4ACR, which codes energy suppliedto section 4-5T from a track battery 4TB, will be seen to be controlledby signal control relay 3HR as well as several other relays.

At intermediate signal location C, a biased track relay TB, is providedwhich relay is responsive to the code transmitted by code transmittingrelay 4ACR over the rails of section 4-5T. Relay 5TB. controls theoperation of a front contact repeater relay 5TFP and these two relaysjointly control the operation of a signal control relay 5HR. Relay 5I-IRcontrols a signal 5S in a manner to be described subsequently,

4 Also found at intermediate signal location 0 are coders 150T and I80CTwhich operate their contacts at code rates of 75 operations per minuteand 180 operations per minute, respectively. Also provided atintermediate signal location C is a code transmitting relay SACR and amagnetic stick relay 5BCR.

At intermediate location C, a pair of track relays BDTR and GHTR, of thebiased type, connected in series and responsive to currents of oppositepolarity are provided. Relay GDTR controls the operation of a frontcontact repeater relay GDTFP and relay BHTR controls the operation offront contact repeater relay GI-ITFP. These four relays control theoperation of a signal control relay BHR, which in turn controls theoperation of signal 68. A code transmitting relay GCTP will code energysupplied from a track battery 6TB to track section G-IT.

At the eastern headblock location E, a track relay 1TB, of the biasedtype, will respond to energy coded by code transmitting relay SCTP andsupplied over the rails of section fi-TT. Relay (TR governs the supplyof energy to a decoding transformer 'ITT which in turn supplies energyto decoding unit IBODU. The decoding unit IBIJDU controls the supply ofenergy to a relay 'lDR, which in turn controls a signal is. Relay 'IDRand a relay 8GP, the control circuits for which are not shown, jointlycontrol a pole changing relay 8DP. A reverse code transmitting relayTRCR is controlled by the track relay lTR.

At each location, energy for the operation of the operation of theapparatus other than the track circuits is furnished by a suitablesource, such as the batteries LB, as shown, the positive and negativeterminals of which are designated by the reference characters B and N,respectively.

As shown, the system is in the condition it normally assumes when thestretch of track is unoccupied. The coders T and IBIJCT located atintermediate signal locations A and C are continuously operating theircontacts at their respective code rates due to the fact that all fourcoders are continuously energized by obvious energizing circuits. Atlocation A, for reasons which will be made clear presently, relay 3DTRis released and relay 3I-ITR is operating its contacts at a code rate oftimes per minute. For reasons which will be made clear subsequently,signal control relay ll-IR is picked up. Accordingly, energy will besupplied to code transmitting relay 3CTP over a circuit which may betraced from positive terminal B of battery LB, over back contact I) ofrelay 3HTR when the contacts of that relay are released, back contact bof relay 3DTR, front contact b of coder IWCT which is operating at a 180code rate, front contact b of relay ll-IR, and the winding of relay 3CTPto negative terminal N of battery LB. Accordingly, relay 3CTP willop-perate its contact a at a 180 code rate. When front contact a ofrelay 3CTP is closed, energy will be supplied from track battery 3TB totrack relay ZTR by a track circuit which may be traced from the positiveterminal of battery 3TB, over front contact a of relay 301?, the rail 2,the winding of track relay ZTR, back contact I) of relay ZRCR and therail I to the negative terminal of battery 3TB. When relay ZTR picks up,a stick circuit including front contact b of relay 2TB. is established,and relay ZTR will remain picked up for the duration of the codeimpulse, after which it will release. Accordingly, relay 2TR willopcrate at a 180 code rate.

With relay ZTR. operating its: contactsat a 180- relay 2D'R to cause thecontacts of relay 2BR to pick up. Therefore, signal 28 will display aclear aspect due to the energization of its green lamp G over a circuitwhich may be traced from, positive terminal B of battery LB; over frontcontact a of relay ZDR, and the green lamp G of signal 28 to negativeterminal N of battery LB. With relay ZDR picked up the energizingcircuit for relay IDP, which circuit may be traced from positiveterminal B of battery LB, over front contact a of relay 1GP, backcontact I) of relay ZDR, and the winding of relay IDP to negativeterminal N of battery LB, will be open at back contact 2) of relay 2BR.In this manner relay IDP will be released, which is the condition inwhich it was described previously.

When the contacts of relay 2TB are picked up an energizing circuit forrelay ZRCR Will be established which may be traced from positiveterminal B of battery LB, over contact a of relay 2TB, and the windingof relay ZRCR to, negative terminal N of battery LB. Accordingly, relayZRCR will be picked up when relay 2TB is picked up. During the off timeof the code lbeing supplied by relay 3TCP, relay ZTR will release andvthereby deenergize relay ZRCR. However, relay ZRCR has a slightly slowrelease characteristic due to the fact that a snubbing circuit for thatrelay will be closed upon the release of relay ZTR. This snubbingcircuit is obvious from an inspection of Fig. 1a and includes backcontact a of relay 2TB. When relay 2TB is released and relay ZRCRremains picked up clue to its slow release characteristic, energy willbe supplied to track relays 3DTR and 3HTR from batter 2TB by a circuitwhich may be traced from the positive terminal of battery 2TB, over backcontact b of relay EDP, front contact a of relay ZRCR, back contact b ofrelay 2TH, the rail I, the windings of relays SHTR and SDIR, [backcontact a of relay 3CTP, the rail 2, and back contact a of relay EDP .tothe negative terminal of battery 2TB. It will be seen that this pulse ofenergy will be supplied to the section 2-3T for a relatively shortperiod of time thereby conserving battery 2TB. The impulse of energytransmitted by relay ERCR will be sufficient to operate the contacts ofrelay 3HTR which, due to its bias, will respond to energy of thepolarity now being supplied from battery 2TB. Accordingly, relay 3HTRwill op-. erate its contacts at a 180 code rate.

At intermediate signal location A, with relay 3HTR operating itscontacts at the 180 code rate and relay 3DTR having its contactsreleased, energy will be supplied to relay SHTFP over a circuit whichmay be traced from positive terminal B of battery LB, over back contacta of relay SDTR, front contact a or relay 3HTR which is operating at a180 code rate, and the winding of relay tl-ZTFP to negative terminal Nof battery LB. Accordingly, relay SI-ITFP will be energized 180 timesper minute. Relay :i'I-I'IFP is provided with a sufiiciently slowrelease characteristic to remain picked up during the off time of theenergy being supplied to it over its previously traced energizingcircuit and, accordingly,. relay 3HTFP will remain picked up as long asthe system remains in the condition, which is now being described. Anenergizing circuit for relay QHR will also be established under thesecondi- Accordingly, sufficient energy will be supplied through decodingunit, IBUDU to tions; This: circuit may be traced from positive terminalB of battery LB, over back contact a of relay 3DTR, back. contact a ofrelay 3HTR which is operating at a 180 code rate, front contact a ofrelay IiHTFP, and the winding of relay 3BR to negative terminal N ofbattery LB; Accordingly, relay 3I-IR will be energized 180 times perminute. Relay 3HR is provided with a sufficiently slow releasecharacteristic to remain picked up during the off time of the energybeing supplied to its winding and, accordingly, relay 3H3 will remainpicked up. It can be seen at this time that signal 38 will display itsapproach aspect due to the energization of its yellow lamp Y by acircuit which may be. traced from positive terminal 3- of battery LB,over front contact b of relay 3HR, back contact b of relay tDTFP, andthe yellow lam Y of signal 38 to negative terminal N of battery LB.

At intermediate signal location 0, it will be subsequently shown thatrelay BHTR is operating its contacts and relay SDTR is released. It willalso be shown presently that relay 5H8. is energized and its contactsare picked up. With these relays in this condition and with coder ECToperating continuously at a code rate, it will be seen that relay ECTPwill be energized at a code rate of 180 times per minute by a circuitwhich may be traced from positive terminal B of battery LB, over backcontact I) of relay SHTR when the contacts of that relay are released,back contact I) of relay BDTR, front contact a of coder l8ilCT which isoperating at a 180 code rate, front contact a of relay 53R, and thewinding of relay ECTP to negative terminal N of battery LB. Therefore,relay ECTP will operate its contact a at a 180 code rate. Accordingly,track relay 'EI'R will be energized at a 180 code rate by energysupplied from track battery 6TB over a circuit which may be traced fromthe positive terminal of battery 6TB, over front contact a of relayECTP, rail 2 in section E-TT, the winding of relay 7TB, back contact aof relay 'IRCR, and rail l in section 6-11 to the negative terminal ofbattery 6TB. Each time relay 'ITR picks up, it establishes a stickcircuit for itself including front contact I) of relay 'ITR. At the endof each code pulse, relay lTR releases its contacts. Accordingly, atthis time relay 1TB, will operate its contacts at a 180 code rate andthereby supply energy to the decoding transformer 'ITT at a 180 coderate. Therefore, decoding unit IBQDU will supply suiiicicntenergy tokeep relay 'IDR picked up. With relay FDR picked up, energy will besupplied to the green lamp G of signal 1S, so that it will show a clearaspect, over a circuit which may be traced from positive terminal B ofbattery LB, over front contact a of relay 'lDR, and the green lamp G ofsignal 75 to negative terminal N of battery LB. With relay 'IDR pickedup the energizing circuit for relay BDP which will be subsequentlytraced, will be open at back contact I) of relay TDR and relay BDP willbe released.

When relay 'ITR. is picked up, an obvious energizing circuit for relay'IRCR including front contact a of relay 1TB, will be established and,accordingly, relay 'lRC-R will pick up. During the oil time of the codesupplied from battery 6TB. to. relay lTR, relay 7TH, will release andopen the energizing circuit for relay 'IRCR at front contact a of relay'lTR. However, a snubbing circuit will be established for relay 'IRCRover back contact a of relay 'i-TR and relay 'iRCR will not immediatelyrelease. During the time that relay ITR is released but relay 'IRCRremains picked up, energy will be supplied from track battery 1TB to thetrack relays SDTR and BI-ITR over a circuit which may be traced from thepositive terminal of battery 1TB, over back contact a. of relay SDP,front contact b of relay IRCR, back contact I) of relay 'ITR, rail I insection 6-1T, the windings of relays GDTR. and BI-I'I'R, back contact aof relay BCTP, rail 2 in section S-TT, and back contact b of relay 8DPto the negative terminal of battery 1TB. It will be seen that relay'IRCR will be picked up and relay 'ITR will be released only for a veryshort time during a code cycle. Accordingly, relatively little energywill [be supplied from battery 1TB to track relays BDTR and BHTR,thereby conserving battery 1TB.

With the relay ,lRCR supplying energy to the section S-TT at a 180 coderate, and the energy being of such polarity that the current will flowthrough relay GI-ITR in the direction necessary for it to operate itscontacts, but not in the direction for relay GDTR to operate itscontacts, it will be seen that relay BHTR will operate its contacts at a180 code rate and relay BDTR will be released. Accordingly, relay EHTFPwill be energized by a circuit which may be traced from positiveterminal B of battery LB, over back contact a of relay BDTR, frontcontact a of relay GHTR which is operating at a 180 code rate, and thewinding of relay BHTFP to negative terminal N of battery LB. RelaySI-ITFP is provided with a slow release characteristic so that it willremain picked up during the off time of the operation of relay GHTR.Accordingly, relay EHTFP will be picked up. With relay BHTR operating inthe manner already described and relay BI-ITFP picked up, it will beseen that relay fiI-IR will be energized by a circuit which may betraced from positive terminal B of battery LB, over back contact a ofrelay SD'I'R, back contact a. of relay BHTR, front contact a of relaySHTFP,

and the winding of relay BHR to negative terminal N of battery LB. Withrelay GDTR, released, the energizing circuit for relay GDTFP, which willbe traced subsequently, will be open at front contact a of relay EDT-R.and relay BDTFP will be released. With the relay BI-IR picked up andrelay BD-TFP released, it will be seen'that signal 63 will display itsapproach aspect due to the energization of its yellow lamp Y by acircuit which may be traced from positive terminal B of battery LB, overfront contact b of relay BHR, back contact b of relay BD'I'FP, theyellow lamp Y of signal 68 to negative terminal N of battery LB.

At intermediate signal location C, let it be assumed that the contactsof relay 5BCR are in their normal or left-hand position and the contactsof track relay 5TH are released. Accordingly, when the contacts of coder1501 are released an energizing circuit will be established for relayEACR which circuit may be traced from positive terminal B of battery LB,over front contact a of relay BHR, back contact I) of relay 5TR, normalcontact of relay BCR, back contact I) of coder 750T, and the winding ofrelay 5ACR to negative terminal N of battery LB. Accordingly, relay 5ACRwill pick up and thereby establish a stick circuit for maintainingitself energized when coder TECT picks up its contacts and opens thepreviously traced energizing circuit for relay EACR. This stick circuitfor relay SACR may be traced from positive terminal B of battery LB,over front contact a of relay GHR, back contact I) of relay 5TH, normalcontact 0 of relay SBCR, front contact 0 of relay 5ACR, and the windingof relay 5ACR to negative terminal N of battery LB. With relay 5AC-Rpicked up, upon the picking up of coder 15CT, an energizing circuit willbe established for energizing relay EBCR so that the position of itscontacts will become reversed. This circuit may be traced from positiveterminal B of battery LB, over front contact I) of relay SACR, frontcontact a of coder 1501, the winding of relay EBCR from right to left,and normal contact a of relay EBCR to negative terminal N of battery LB.Accordingly, relay 5BCR will operate its contacts to their reverseposition. The reversal of contact c of relay 5BCR opens the previouslytraced pick up and stick circuit for relay 5ACR but relay 5ACR. remainsenergized at this time by a second stick circuit including front contacta of relay BHR, back contact I) of relay 5TH, front contact I) of coder150T, and front contact 0 of relay 5ACR. Upon relay EBCR reversing itscontacts, a track circuit will become established for supplying energyfrom track battery 5TB to track relay MR. This circuit may be tracedfrom the positive terminal of battery 5TB, over reverse contact I) ofrelay BBCR, front contact a of relay EACR, rail 1 in section l-ET, backcontact a of relay iACR, the winding of relay 4TB, and rail 2 in sectionit-5T to the negative terminal of battery 5TB. Accordingly, relay 4TBwill pick up. When coder TSC'I releases, the second stick circuit forrelay EACR will become open at front contact I) of coder TECT andaccordingly relay EACR will release. The release of coder 150T will alsoopen the energizing circuit for relay EBCR. However, the contacts ofrelay EBCR will remain in their reverse position due to the magneticstick characteristic of relay 5BCR. Upon coder 150T again picking up, acircuit for energizing relay BBCR, so that its contacts will operate totheir normal position will become established. This energizing circuitmay be traced from positive terminal B of battery LB, over reversecontact a of relay BBCR, the Winding of relay EBCR, from left to right,front contact a of relay EECT, and back contact b of relay 5ACR tonegative terminal N of battery LB. Accordingly, relay 513GB will operateits contacts to their normal position. In this manner it can be seenthat energy will be supplied to the rails of section ll-5T from trackbattery 5TB when and only when relay 5ACR is picked up and relay 5BCR isin its reverse position. From the above description, it should be clearthat this condition will occur during only one-half cycle of theoperation of the coder 150T out of two cycles of operation of thatcoder. Therefore, code will be supplied at a rate of thirty-seven andone-half times per minute with the on time of that code being one-fourthof the total time for the thirty-seven and one-half code cycle. In thismanner appreciable energy will be saved since the drain on track battery5TB will be one-half of the drainage which would occur if section 4-51was energized at a code rate.

In the above described manner it will be seen that track relay 4TR willbe responding to energy being coded at a thirty-seven and one-half coderate and in this manner will supply energy to relay GTFP at athirty-seven and one-half code rate over a circuit which may be tracedfrom positive terminal B of battery LB, over front contact a of relay4TB which is operating at a thirty-seven and one-half code rate, and thewinding of relay 4TFP to negative terminal N of battery LB. Relay 4TFPhas a sufficiently slow release characteristic so that it will notrelease during the off time of the thirty-seven and onehalf code.Accordingly, with relay 4TB so operating, relay lTFP will remain pickedup. Furthermore signal control relay 4BR will be energized at athirty-seven and one-half code rate over a circuit which may be tracedfrom positive terminal B of battery LB, over back contact a of relay4TB, front contact a of relay iTFP, and the winding of relay ll-IR tonegative ter minal N of battery LB. Relay 411R is also provided with aslow release characteristic suilicient to maintain it picked up duringthe off time of the supply of energy to that relay. Accordingly, relaytI-IR will be picked up at this time. With relay EHR picked. up, energywill be supplied to the green lamp G of signal ts so that it willdisplay a clear aspect by a circuit which may be traced from positiveterminal B of battery LB, over front contact of relay lHR, and the greenlamp G of signal lS to negative terminal N of battery LB.

Each time relay lTR picks up, a circuit will be established for acharging capacitor Q and this circuit may be traced from positiveterminal B of battery LB, over front contact b of relay 4TB, frontcontact 17 of relay lTFP, resistor R, and capacitor Q to negativeterminal N of battery LB. Upon the release of relay 4TB, a circuit willbe established for connecting capacitor Q across the winding of relayiACR and upon this circuit being established sufficient energy will besupplied from capacitor Q to the relay 4ACR, to cause relay @ACR to pickup its contact for a short period of time. This circuit connecting thecapacitor Q across the winding of relay AAC R may be traced from theright-hand terminal of the capacitor Q, through resistor R, frontcontact b of relay dTFP, back contact b of relay lTR, front contact a ofrelay 3H3, and the winding of relay lACR to the left-hand terminal ofcapacitor Q. Accordingly, relay EACR will pick up its contacts andestablish a circuit for supplying energy from track battery lTB to trackrelay ETR which circuit may be traced from the positive terminal ofbattery 4TB, over front contact a of relay lACR, rail I in track section5-51, back contact a of relay EACR, the winding of relay 5TB, and rail 2in track section 4-51 to the negative terminal of battery 6TB. It willbe seen that relay dACR will be energized at the same code rate thattrack relay 4TB is being energized, that is, thirty-seven and one-halftimes per minute. Accordingly, relay 5TB will be energized at this samethirty-seven and one-half code rate. In this manner the drain on battery4TB is kept to minimum during this normal unoccupied condition. Itshould be pointed out that resistor R is included in these circuits inorder to limit cur rent flow and reduce contact arcing.

As was already stated, the on time of the normal thirty-seven andone-half code is approximately 25% of the total time for a thirty-sevenand one-half code cycle. Capacitor Q and relay dACR are so proportionedthat the on time of the reverse thirty-seven and one-half code is lessthan 25% of the thirty-seven and one-half code cycle so that the totalon timeof the normal and reverse thirty-seven and one-half codes is lessthan 50% of the time for a thirty-seven and onehalf code cycle. Withsuch a short total on time, the well known track storage current effect10 will be minimized. However, the on time of the normal and reversethirty-seven and one-half "codes are of 'sufiicient duration to reliablyfeed through at least three frontcontact repeating cut sections, itneeded, without excessive code distortion. This feature is of greatbenefit from an economic view-point, since the from; contact repeat-mgout section, as is well known in the art of railway signaling, requiresmuch less apparatus, is much simpler, and is less costly than any othertype of coded track'cut section or code gencrating location.

With relay 5TB operating at a thirty-seven and one-half code rate, relayETFP will be energized thirty-seven and one-half times per minute over acircuit including front contact a of relay 5TB. Relay is provided with asufiiciently slow release characteristic to remain picked up during "theoil periods of its energization and, accordingly, with relay 5TB,operating at a thirty-seven and one-half code rate, relay STEP willremain picked up. With relay BTFP picked up, relay EI-IR will beenergized thirtyseven and one-half times per minute over a circuit whichmay be traced from positive terminal B of battery LB, over back contacta of relay 5TB which is operating at a thirty-seven and onehalf coderate, front contact a of relay 5TFP, and the winding of relay EHR 'tonegative terminal N of battery LB. Relay ill-IR has a sufiiciently slowrelease characteristic to remain picked up during the "off period of its'energizati'on. Accordingly, with relay 5TB operating at a thirty-sevenand one-half code rate, relay BI-IR will remain picked up. With relay5I-I'R energized, signal 5S will display "a clear aspect due to theenergization of its green lamp G by an obvious circuit including frontcontact h of relay SHR. The code assignments for the several tracksections and the aspect displayed by the various signals when thestretch is in its normal unoccupied condition is shown in Figs. 2a andBut.

My system is so arranged that when a train occupies a particularsection, regardless of the direction the train is moving, the codeassignments and signal aspects will be the same. When a train occupiesthe western passing siding, signal IS will display a stop 'or red aspectand relay IGP will become released. This, however, will have no effectupon the remainder of the system since with the relay 1GP released, thecircuit for energizing relay IDP will merely become open at anadditional point and therefore relay IDP will remain released.Accordingly, the remainder of the system will maintain its originalcondition. Therefore, the system will assume the condition shown in Fig.2b and Fig. 3f.

The condition thes'ystem assumes when atrain occupies section2-3T isshown in Figs. 2c and 301. When a train occupies section 2-3T, signal ISwill be clear ad relay IGP will be picked up. Any energy being suppliedtosection 2-3T willbe shunted by the wheels and axles of the train, andaccord.- ingly, track relays 2TB, 3DTR and 3HTR will be released. .Aswill subsequently be seen, energy at a18'0 code rate will be supplied tosection Z-ST by code transmitting relay 3CTP. With track relay 2'IRreleased, code transmitting relay 2RCR will also be released. Therefore,no reverse code will be supplied to section 2-3'1. Furthermore, withtrack relay 2TH, released no coded energy will'b'e supplied to decodingtransformer 2TT and, accordingly, no energy willbe supplied to thedecoding unit iDU. Therefore, relay ZDR will be released and establishan obvious circuit for energizing the red lamp R of signal 23. Withrelay 2DR released, an energizing circuit will be established forsupplying energy to relay 1 DP, which circuit may be traced frompositive terminal B of battery LB, over front contact a of relay I GP,back contact I) of relay ZDR, and the winding of relay IDP to negativeterminal N of batteryLB. Accordingly, relay l DP will be picked up butthis will have no effect upon the circuit arrangement. At intermediatesignal location A, with track relays 3DTR and 3I-ITR both released,relays 3DI'FP, 3I-ITFP, and BHR will all be released. Upon the releaseof relay 3HR, an obvious circuit for energizing the red lamp R of signal3S will become established, which circuit includes back contact b ofrelay 3BR.

With relay BHR released, the previously traced circuit for dischargingcapacitor Q through the winding of relay 4ACR will be open at frontcontact a of relay SI-IR. Accordingly, no energy will be supplied fromthe capacitor Q to relay 4ACR and that relay will be released.Therefore, no energy will be supplied from battery 4TB to track relay5TB. since that track circuit will be opened at front contact a of relay4ACR. Accordingly, relay 5TB will be released and stay released.Therefore, at intermediate signal location C, relay STFP will bereleased since it is not being supplied with energy over front contact aof relay 5TB, and with relay ETF'P released, relay SHE will be releasedand thereby establish a circuit for energizing red lamp R. of signal 58over back contact I) of relay SI-IR. The release of relays 5TB, and SHR,will have no efiect upon the generation of thirty-seven and one-halfcode as was explained at the end of the description of the system in itsnormal unoccupied condition. Accordingly, thirty-seven and one-half codewill be transmitted from track battery 5TB to track relay 4TB over frontcontact a of code transmitting relay 5ACR and in this manner relay 4TBwill operate as it did during the time the track stretch was unoccupied.Therefore, relays ATP? and lHR will be energized and picked up.Accordingly, signal 43 will display a clear aspect due to theenergization of the green lamp G over front contact of relay ll-IR in amanner already described.

Furthermore, with relay 4HR picked up, energy at a180 code rate will besupplied to relay SCTP by a circuit which may be traced from positiveterminal B of battery LB, over back contact b of relay 3HTR, backcontact I) of relay tDTR, front contact b of coder I80CT which isoperating at a 180 code rate, front contact I) of relay ll-IR, and

the winding of relay 3CTP to negative terminal N of battery LB.Therefore, relay 3CTP will operate its contact at a 180 code rate totransmit 180 code to section 2-3T. Of course, as was described earlier,the code being transmitted to section 2-3T by relay 3CTP will be shuntedby the wheels and axles of the train occupying the section.

With relay HR released, a circuit is established for supplying energy tocode transmitting relay GCTP which circuit maybe traced from positiveterminal B of battery LB, over front contact 0 of coder 75CT, backcontact a of relay 5I-IR, and the winding of relay BCTP to negativeterminal N of battery LB. Accordingly, relay BCTP will operate at a 75code rate and supply energy to track relay lTR over a track circuitwhich may be traced from the positive terminal of track battery 6TB,over front contact a of relay BCTP which is operating at a 75 code rate,rail 2 in section 6-1T, through the winding of relay 'ITR, back contacta of relay 'IRCR, rail l in section 6-IT, to the nega- 12 tive terminalof track battery 6TB. Accordingly,

relay 'ITR will operate at a '75 code rate.

Because relay 'ITR is operating at a '75 code rate, insuflicient energywill be supplied from the decoding unit IBUDU to relay IDE to keep thatrelay picked up. Accordingly, relay lDR. will be released and therebyestablish a circuit including back contact a of relay IDR for energizingred lamp R of signal is. Furthermore, with relay l'DR. released, relay'8DP will become energized by a circuit which may be traced frompositive terminal B of battery LB, over front contact a of relay 8GP,back contact b of relay 'IDR, and the winding of relay 8DP to negativeterminal N of battery LB. In this manner the polarity of the reversecode being supplied from track battery 1TB to section B-lT in a mannerto be described below Will be the reverse of the polarity of the codetransmitted by relay TRCR. when the stretch is unoccupied.

Upon relay lTR picking up during the "on time of the code being suppliedby code transmitting relay BCTP, a circuit for energizing relay 'lRCRwill become established, which circuit includes front contact 'a ofrelay lTR. During the off time of the code being supplied to relay lTR,relay lTR will release. Relay lRCR will remain picked up for a shorttime due to its slow release characteristic. However, the slow releasecharacteristic of relay 'IRCR. will not be sufiicient to maintain itpicked up until relay lTR becomes reenergized and, accordingly, relaylRCR will finally release. During the interval between the release ofrelay 'ITR and the release of relay IRCR, energy will be supplied fromtrack battery 7TB to track relays BDTR and GHTR over a track circuitwhich may be traced from the positive terminal of track battery 1TB,over front contact I) of relay SDP, rail 2 in section G-IT, back contacta of relay BCTP, the windings of relay BHTR. and GDTR, rail I in sectionfi-lT, back contact b of relay 'ITR, front contact b of relay 'IRCR, andfront contact a of relay BDP to the negative terminal of battery 1TB. Itwill be seen that the on time of this code being supplied from battery'lTB will be relatively short in comparison to its off time and, in thismanner, appreciable saving in wear on battery lTB may be achieved aswell as a reduction in track storage current effect. It will also beseen that the code rate at which energy will be supplied from battery1TB to track relays BDTR. and fil-ITR will be at a 75 code rate.

With the reverse code being transmitted to section B-lT now being ofsuch polarity that rail I is negative and rail 2 positive, relay BDTRwill be operating at a 75 code rate and relay EHTR, will be released andremain released. Accordingly, relay BI-ITFP will be released but relayGDTFP will now be energized 75 times per minute over front contact a ofrelay EDTR. Relay @DTFP is provided with a sufficiently slow releasecharacteristic to remain energized during the off time of the energybeing supplied to it and, accordingly, relay BDTFP will pick up and staypicked up. Therefore, energy will be supplied to relay GHR over acircuit which may be traced from posof the energy being supplied to itand, accordingly, relay BDTFP will pick up and stay picked up.Therefore, energy will be supplied to relay itive terminal B of batteryLB, over back contact a of relay BDTR which is operating at a '75 coderate, back contact a of relay BHTR, front contact a of relay BDTFP, andthe winding of relay BHR to negative terminal N of battery LB.

Accordingly, relay tI-IR will remain picked up. With relay tD'I'FP nowpicked up, it will be seen that energy will be supplied to the greenlamp G of signal 68 over a circuit which may be traced from positiveterminal B of battery LB, over front contact I) of relay GHR, frontcontact b of relay BDTFP, and green lamp G of signal 68 to negativeterminal N of battery LB.

The condition the system assumes when a train occupies section sl-T isshown in Figs. 2d and 3d. When a train occupies section ii-5T, anyenergy being supplied to that section will be shunted by the wheels andaxles of the train and track relays 4TB. and 5TB will therefore bereleased. As will be shown subsequently, thirtyseven and one-half codeis being supplied to section 4-5T at location C and ninety code is beingsupplied to section 6-51 at location A. With relay lTR released, relayiTFP and relay ll-IR will be released. With relay lHR released, anobvious circuit will be established for energizing the red lamp R ofsignal is. With relay 5TB, released, relays E'IFP and 5BR will bereleased and, accordingly, an obvious energizing circuit will beestablished for the red lamp R, of signal ES.

With relay AHR released, 'a circuit will be established for energizingrelay SCTP at a 75 code rate, which circuit may be traced from positiveterminal B of battery LB, over front contact a of coder 750T, backcontact b of relay 451R, and the winding of relay $01? to negativeterminal N of battery LB. Accordingly, relay 301? will be energized 75times per minute and will therefore code energy supplied from trackbattery 3TB to track relay 2TB at a 75 code rate. With relay ZTR beingenergized at a 75 code rate, decoding unit liiilDU will not supplysuflicient energy to relay ZDR to pick it up and, accordingly, it willremain released and maintain the circuit for energizing the red lamp Rof signal 2S. Furthermore, with relay ZDR released, relay ID]? willremain energized and a reverse code of '75 pulses per minute will betransmitted from track battery 2TB to track relays SDTR and SI-ITR in amanner similar to that already described. With relay iDP picked up, thisreverse '15 code will be of such polarity that rail I will be energizednegatively and rail 2 positively and, therefore, relay SDTR will beoperating at a 75 code rate and relay EHTR will be released.Accordingly, relay 3HTFP will be released but relay 3DTFP will beenergized over a circuit which may be traced from positive terminal B ofbattery LB, over front contact a of relay SDTR which is operating at a75 code rate, and the winding of relay SDTFP to negative terminal N ofbattery LB. Relay 3DTFP is provided with a slow release characteristicso that it will remain picked up during the OK time of the coded energybeing supplied to it. Accordingly, relay SDTFP will remain picked up andthereby establish an energizing circuit for relay 3'HR which circuit maybe traced from positive terminal B of battery LB, over back contact a ofrelay BDTR which is operating at a 75 code rate, back-contact a of relaySI-1TB, front contact a of relay SDTFP, and the winding of relay 3BR tonegative terminal N of battery LB. As was stated earlier, relay 3BR isprovided with a sufiiciently slow release characteristic to remainpicked up during the off time of the energy being supplied to it.Accordingly, relay 3HR will remain picked up and establish an energizingcircuit for the green lamp G of signal 38 which circuit may be tracedfrom positive terminal B of battery LB, over front c'on- 14 tact b ofrelay 3HR, front contact b of relay 3DTFP, and the green lamp G ofsignal 38 to negative terminal N of battery LB.

With relay SHR energized, its contacts are picked up. Let it be assumedthat relay 4ACR is released and relay lB'CR has its contacts in theirreverse or right-hand position. Furthermore, let it be assumed that atthis instant coder 18001 is released. Upon coder IBll'CT picking up a,circuit will be established for energizing relay tBCR so that it willoperate its contacts to their normal position. This circuit may betraced from positive terminal B of battery LB, over reverse contact a,of relay 436R, the winding of relay lBCR from left to right, frontcontact a of coder lBtCT, and back contact 17 of relay lACR to negativeterminal N of battery LB. Accordingly, relay iBCR will operate itscontacts to their normal position. Upon the release of coder EBGCT, theenergizing circuit for relay ABCR will become open at front contact a ofcoder liltCT, but the contacts of relay 4BCR will remain in their normalposition due to the magnetic stick characteristic of relay GBCR.Furthermore, when coder ICT releases, a circuit will be established forenergizing code transmitting relay lACR which circuit may be traced frompositive terminal B of battery LB, over normal contact I) of relay HBCR,back contact I) of coder IBGCT, back contact b of relay 4TFP, backcontact I) of relay 4TB, front contact a of relay can, and the windingof relay 4ACR to negative terminal N of battery LB. Accordingly, relayAACR will pick up and thereby establish a track circuit for supplyingenergy from track battery MB to track relay 5TB, which circuit may betraced from the positive terminal of battery 4TB over front contact a ofrelay lACR, rail I in section l -5T, back contact a of relay EACR, thewinding of relay 5TB, and rail 2 in section "t-liT to the negativeterminal of battery 4TB. Upon the picking up of coder IBBCT a secondtime, relay QACR will continue to be energized by a stick circuit whichmay be traced from positive terminal B of battery LB, over normalcontact b of relay tBCR, front contact 0 of relay AACR, back contact 2)of relay 4TFP, back contact 1) of relay lTR, front contact a of relay3HR, and the winding of relay 4ACR, to negative terminal N of batteryLB. Accordingly, relay AACR will continue to remain picked up andthereby provide a circuit for continuing the supply of energy to trackrelay 5TB, from battery 4TB. Furthermore, upon the second picking up ofcoder lBilCT, with relay lACR now stuck up, a circuit will beestablished for energizing relay 4BCR, so that its contacts will operateto their reverse position. This circuit may be traced from positiveterminal B of battery LB, over back contact a of relay ii-IR, frontcontact I) of relay AACR, front contact a of coder IBOC'I, the windingof relay tBCR from right to left, and normal contact a of relay ABCR tonegative terminal N of battery LB. Accordingly, relay ABCR. will operateits contacts to their reverse position. However, relay QACR will notrelease because it will continue to remain energized by a second stickcircuit which may be traced from positive terminal B of battery LB, overfront contact I) of coder lfiilCT, front contact c of relay GACR, backcontact I) of relay 4TF'P, back contact I) of relay 4TB, front contact aof relay 3I-IR and the winding of relay '4ACR, to negative terminal N ofbattery LB. Upon coder IBOCT releasing a second time, the second stickcircuit for relay AACR will become open at front contact I) of coder IBUCT, relay 4ACR will release and the cycle will be repeated. It will beseen from the above explanation that code transmitting relay lACR willremain picked up during a cycle of operation of coder I80CT and relay4ACR will remain released during a cycle of operation of coder IBBCT.Accordingly, the code transmitting relay tACR will be operating at aninety code rate and transmitting energy to section 4-5T at that coderate. However, if, as supposed, a train is occupying section 4-5T, thewheels and axles of the train will shunt this energy.

With relay SHE released, energy will be supplied to code transmittingrelay BCTP at a 75 code rate over a circuit which may be traced frompositive terminal B of battery LB, over' front contact of coder lCT,back contact a of relay SHR, and the winding of relay SCTP to negativeterminal N of battery LB. Accordingly, energy will be supplied fromtrack battery 5TB to track relay TIR at a code rate of '75 times perminute over front contact a of relay BCTP. Therefore, track relay TTRwill operate at a 75 code rate which will result in relay 'IDR beingreleased and the red lamp R of signal IS being energized. Furthermore,code transmitting relay TRCR. will transmit a reverse code in a mannersubstantially the same as that already described when a train occupiedsection 23T and this energy will cause relay GDTR to operate and relayBHTR to remain released. Therefore, relays GD'IFP and BHR will be pickedup. Accordingly, in a manner similar to that described when a trainoccupied section 2-3T, signal 68 will display a clear aspect.

With relay BI-IR picked up, energy will be supplied to relays 5ACR and53GB in a manner already described and, accordingly, relay 5ACR willtransmit thirty-seven and one-half code to section 4-5T. Of course, witha train in section 4-5T, this energy will be shunted by the wheels andaxles of the train.

One of the main advantages of my system is utilizing opposing codes ofdifferent slow code rates. As was pointed out earlier, using athirtyseven and one-half normal and reverse code with a total on time ofless than 50% minimizes track storage current effect in track circuits,but still permits the use of several cut sections in section t-ST. Witha train occupying the section 4-5T,

both thirty-seven and one-half and ninety codes are supplied so thatupon the train vacating the section, the transmitting apparatus at bothends cannot get into synchronism but will reset in a relatively shorttime so that the system will operate in the prescribed manner.

Figs. 2e and show the condition of the system when a train occupiessection 6-lT. When a train occupies section G-IT, any energy beingtransmitted to the track rails in that section will be shunted by thewheels and axles of the train and track relays 'ITR, BI-ITR and BDTRwill therefore be released. As will be shown presently, energy at a 180code rate will be supplied to section 6-1T from location C. With relay1TB, released, no energy will be supplied to relay TRCR, and it too willbe released. Accordingly, no reverse code will be supplied to sectionG-lT. Furthermore, no energy will be supplied to decoding transformer'ITT and, accordingly, no energy will be supplied to relay 'IDR.Therefore, relay FDR will also be released and thereby establish acircuit for maintaining the red lamp R of signal 1S energized.

At signal location C, with track relays GDI'R l6 and GHTR released,relays BDTFP, BHTFP and BHR will all be released. Accordingly, a circuitwill be established for energizing the red lamp R of signal 6S whichcircuit includes back contact b of relay BHR.

With relay BHR released, the previously traced energizing circuit forsupplying energy to code transmitting relay SACR will be open at frontcontact a of relay BHR. Accordingly, no energy will be supplied fromtrack battery 5TB to the rails of track section 4-5T from the east endof the section. Therefore, at signal location A, track relay 4TB will bereleased. With relay 4TB released, no energy will be supplied to relaylTFP over front contact a of relay 4TB, and relay 4TFP will be released.With relay 4'I'FP released, the previously traced energizing circuit forrelay AHR will be open at front contact a of relay 4TFP and relayAI-IR,will be released. Accordingly, the red lamp R of signal 48 will beenergized over an obvious circuit.

With relay II-IR released, a circuit will be established for supplyingcoded energy at a '75 code rate to code transmitting relay 3CTP. Thiscircuit may be traced from positive terminal B of battery LB, over frontcontact a of coder 750T, back contact b of relay lHR. and the winding ofrelay BCTP to negative terminal N of the battery LB. Accordingly, relay3CTP will operate its contacts at a code rate and coded energy is thussupplied from track battery 3TB to track relay ZTR. at a 75 code rate.Therefore, track relay 2TB will operate at a 75 code rate. With relay2TB so operating, insuflicient energy will be supplied to relay ZDR tocause it to pick up. Therefore, signal 23 Will display a red aspect aspreviously described.

Furthermore, with relay 2TB operating at a 75 code rate, relay ZRCR willtransmit a reverse code at a '75 code rate as was previously described.The polarity of the code being transmitted by relay ZRCR from battery2TB will be such that rail 2 will be energized with energy of positivepolarity and rail l with energy of negative polarity. Accordingly, atsignal location A, relay 3DTR will operate and relay 3I-ITR will bereleased. Therefore, relay SDTFP will be picked up and relay SHR willalso be picked up. With relay SHR picked up and relay SDTFP picked up,the circuit for energizing the green lamp G of signal 38, which hasalready been traced, will remain closed.

Furthermore, with relay 3HR picked up, the previously traced circuitsfor controlling relays lACR and 4BCR will be established and relay 4ACRwill transmit ninety code in a manner already described. Therefore, atlocation C, relay 5TH will commence operating at a ninety code rate andthereby energize relay 5TFP ninety times per minute over an obviouscircuit including front contact a of relay 5TB. Because of the slowrelease characteristic of relay ETFP, it will remain picked up duringthe off time of its energization. Accordingly, in a manner alreadydescribed, relay 51-11% will pick up and establish an obvious energizingcircuit for green lamp G of signal 58.

With relay til-IR picked up, the previously traced energizing circuitfor supplying energy to relay GCTP at a 75 code rate will beestablished. Accordingly, relay GCTP will transmit '75 code to sectionE-lT but, of course, with a train occupying the section, this energywill be shunted by the wheels and axles of the train.

When a train occupies the eastern passing 17' siding E signal as willdisplay its stop or red aspect and relay 8GP will be released.Therefore, the previously traced energizing circuit for relay 8DP willbe open at front contact a of relay 8GP and, accordingly, relay EDP willbe released. Furthermore, with a train in the eastem passing siding E,130 code will be transmitted by relay ECTP in a manner identical to thatdescribed for the normal condition and will be received by track relay"IIR, which will operate in a 180 code rate. Accordingly, relay 'IRCRwill operate at 180 code rate and transmit a reverse 180 code ofpolarity such that rail 2 is energized with energy of negative polarityand rail I is energized with energy of positive polarity, in a mannersubstantially the same as described for the normal unoccupied condition.Therefore, relay GHTR will operate at a 180 code rate and relay GDTRwill remain released. Acoord ingly, signal 68 will display its yellowaspect as previously described. With relay SHTR operating, relay (SI-1Rwill once more pick up and enable relay 'EACR to transmit thirty-sevenand one-half code as already described. Therefore, at location A, relay4TB. will operate at a thirtyseven and one-half code rate, and in amanner substantially like that described for the normal condition, relaylACR will transmit a reverse,

thirty-seven and one-half code to track relay 5TH. With relay 4TB sooperating, relay ll-IR will be picked up and thereby establish a circuitfor energizing relay 301? 180 times per minute. Accordingly, relay 3CTPwill transmit 180 code to relay ZTR which will operate its contacts 188times per minute. Relay ZRCR will operate its contacts 180 times perminute and thereby transmit a reverse code, with rail l energizedpositively and rail 2 energized negatively, to relay ZiHTR. It can beseen from the description that when a train occupies the eastern passingsiding E, the system is in its normal condition with the exception ofsignal 88 which will indicate stop. The signal aspects and codeassignments for the system when a train occupies eastern passing sidingE are shown in Figs. 2 f and 3b.

Having described the operation of my novel system when a train,traveling either eastbound or westbound, occupies the various sectionsin the stretch, let it now be assumed that a train approaches thestretch of track moving in an eastbound direction. When the train is inthe western passing siding W and approaches the stretch of single track,signal is will display a stop or red aspect and relay iDP will becomereleased. This, however, will have no effect upon the remainder of thesystem since, with relay IDP released, the circuit for energizing relayEDP will become open at an additional point and therefore relay ID? willremain released. Accordingly, the remainder of the system will remain inits original condition. The various code assignmerits and signal aspectswhen a train traveling in an eastbound direction occupies the westernpassing W are shown in Fig. 212.

When an eastbound train enters section 2-3T, and leaves the westernpassing siding W, signal IS will clear up and relay IGP will pick up andboth will stay in this condition for the remainder of the eastboundmovement, assuming a following eastbound train does not occupy thewestern passing siding W. With a train in section 23T, any energy beingsupplied to that section will be shunted by the wheels and axles of thetrain and, accordingly, relays 2TB, BDTR and SHTR will release.Therefore, relays 3DTFP and 3HTFP will release, as will relay 3HR.Accordingly, signal 38 will display its red aspect. Furthermore, withrelay 3I-IR released, the previously traced energizing circuit for relayMECR will become open at front contact a of relay 3HR and relay 4ACRwill release. Therefore, no energy will be supplied to section l-ET overfront contact a of relay lACR and, accordingly, relay 5TR will release.

With relay 5TB released, relays ETFP and SHR will become deenergized andthey too will release. With relay 5HR released, signal 55 will display ared aspect. Furthermore, with relay 5BR released, an energizing circuitfor supplying 75 code to code transmitting relay BCTP will becomeestablished which circuit may be traced from positive terminal B ofbattery LB, over front contact c of coder T, back contact a of relaySHR, and the winding of relay BCTP to negative terminal N of battery LB.Accordingly, relay 'BCTP will commence operating its contact at a 75code rate and transmit energy at that code rate from battery 6TB totrack relay 'ITR. In the manner already described, with relay 'ITRoperating at a 75 code rate, relay IR-CR will also operate at a 75 coderate and these two relays together will generate and transmit a '75reverse code to section B-lT. Because relay 'ITR is oper-- ating at a'75 code rate, insuificient energy will be supplied to relay IDE to keepit picked up and it will be released. Therefore, signal 18 will displayits red aspect. Furthermore, with relay 'iDR released, relay 8D willbecome energized by a circuit which may be traced from positive terminalB of battery LB, over front contact a of relay 8GP, back contact b ofrelay "DR, and the winding of relay BDP to negative terminal N ofbattery LB. Accordingly, relay 8UP will pick up, thereby causing thereverse 75 code being transmitted to section B-lT by relay TRCR to be ofsuch polarity that rail 2 will be energized positively and rail lenergized negatively.

With section (l-TT being so energized, relay BDTR will commenceoperating at a "/5 code rate and relay GHTR will release. Accordingly,in

'a manner already described, relay GDTFP will become picked up and relayGHR will remain energized. Therefore, signal 68 will display a greenaspect due to energization of its green lamp G by a circuit includingfront contact b of relay BER and front contact I) of relay BDTFP.

With relay tI-IR picked up, relays 5ACR and EBCR will continue to beenergized in such a manner as to generate thirty-seven and one-half codeand transmit that code to section d-BT. A detailed description of thegeneration and transmission of thirty-seven and one-half code at signallocation 0 has previously been made. Accordingly, at signal location A,track relay 4TB will continue operating its contacts at a thirtysevenand one-half code rate and, in a manner already described, relaysQ'ITE'P and 4BR will remain picked up. With relay 4HR picked up, signal4s will display a green aspect due to the energization of its green lampG by an obvious circuit including front contact 0 of relay ll-IR.Furthermore, with relay lHR picked up, code transmitting relay 3CTP willbe energized times per minute by a circuit which may be traced frompositive terminal B of battery LB, over back contact I) of relay BHTR,back contact b of relay 3DTR, front contact b of coder [800T which isoperating at a 180 code rate, front contact b of relay 4HR, and thewinding of relay 3CTP to negative terminal N of battery L13.Accordingly, relay SCTP will code energy being supplied from trackbattery 3TB to section 2-31 by its front contact a at a 180 code rate.However, with a train occupying section 2-31, the energy being coded byrelay SCTP will be shunted by the wheels and axles of the train and,therefore, relay 2TB will be released. With relay 2TR released, relayZRCR. will be released and no reverse code will be transmitted tosection 2-31. Furthermore, with relay 2TH released, relay 2DR will bereleased, and signal 23 will therefore display its red aspect. The codeassignments and signal aspects in my system when an eastbound trainoccupies section 2-312 are shown in Fig. 20.

When the eastbound train vacates section 2-3T and occupies section 4-5T,any energy being supplied to section 4-5T will be shunted by the wheelsand axles of the train and, accordingly, relay lTR will release andrelay 5TB will remain released. With relay GTE released, relays QTFP andGHR will release and thereby establish a circuit for energizing the redlamp R of signal is, which circuit includes back contact of relay ll-IR.Furthermore, with relay 3HR now released, relay SCTP will commence beingenergized at a 75 code rate by a circuit which may be traced frompositive terminal B of battery LB, over front contact a of coder lSCTwhich is operating at the 75 code rate, back contact I; of relay QHR,and the winding of relay 3CTP to negative terminal N of battery LB.Accordingly, relay 3CTP will code energy supplied from track battery 3TBto track relay 2TB in a manner already described and relays 2TB- andZRCR will commence operating at a 75 code rate. As was explainedearlier, with relay 2TB operating at a 75 code rate, relay ZDR will bereleased and signal 25 will display a red aspect. As was stated earlier,signal IS is displaying its clear aspect and relay iGP is picked up.With relay ZDR released, a circuit will be established for energizingrelay lDP, which circuit may be traced from positive terminal B ofbattery LB, over front contact a of relay IGP, back contact b of relayZDR, and the winding of relay IDP to negative terminal N of battery LB.Accordingly, relay IDP will pick up and establish a circuit so that thereverse code being supplied to section 2-3T will be of such polaritythat rail 2 will be energized positively and rail i will be energizednegatively. Therefore, at signal location A, relay 3DTR will commenceoperating and relay BHTR will remain released. Accordingly, relay BDTFPwill pick up and establish an energizing circuit for relay 3HR whichwill also pick up. There fore signal 38 will display its green aspectdue to energization of the green lamp G by a circuit including frontcontact b of relay 3HR and front contact b of relay 3DTFP.

With relay 3HR now picked up, relays EACR and lBCR will commenceoperating in a manner already described to generate and transmit 90 codeto section l-ET. However, with the train now occupying section ii-T,this energy will be shunted by the wheels and axles of the train and,accordingly, relay 5TB will remain released. Therefore, relays 5TFP andEHR will remain released and signal 53 will continue to display its redaspect. Furthermore, with relay 5H3 still released, relay ECTP willcontinue to be energized at a 75 code rate, as was previously described,and relays TTR and lRCR will con tinue to operate at a 75 code rate andtransmit a reverse code to section Ei-lT with rail 2 energizedpositively and rail I energized negatively.

20' Therefore, at the eastern passing siding E, relay TDR will remainreleased and signal IS will continue displaying its red aspect.

At signal location C, relay GDTR will continue to operate at a code rateand relay BHTR will remain released. Therefore, signal EDTFP will remainpicked up, relay SHTFP will remain released and relay SHR. will remainenergized. Therefore, signal BS will continue to display its greenaspect. Furthermore, with relay GHR picked up, relays EBCR and EACR willcontinue to operate in a manner already described so that they willcooperate to generate and transmit thirty-seven and one-half code tosection l-ET. However, this energy will be shunted by the wheels andaxles of the train now occupying section 4-5T and, as was alreadydescribed, relay B'I'R will remain released. It should be noted, as thetrain vacates section 4-5T, the code and the thirty-seven and one-halfcode will scramble, and because of the different code rates the systemwill reset itself so that it will continue to operate in the prescribedmanner in a relatively short time. If the codes were at the same coderate, it would be possible for the code transmitters at both ends ofsection l-ET to get into synchronism in which condition they mightremain for an extended period of time. If this were the case, theremaining portions of the system would not function properly for anextended period of time. The code assignments and signal aspects in mysystem when an eastbound train occupies section 4-5T are shown in Fig.2d.

When the eastbound train vacates section l-ET and occupies sectionB-l'I, any energy being supplied to section fi-TT will be shunted by thewheels and axles of the train and, accordingly, relays ITR, BDTR andBH'IR will all be released. Therefore, relays SDTFP and SHR will releaseand signal 6S will display its red aspect. Furthermore, with relay BI-IRreleased, no energy will be supplied to operate relays 5ACR. and 5BCR inthe manner already described for generating and transmittingthirty-seven and one-half code and, accordingly, no energy will besupplied to section 4-5)? at signal location C.

Accordingly, at signal location A, relays 4TR, ITFP and IHR will remainreleased and signal 45 will continue to display its red aspect. Withrelay 4HR released, relay 3CTP will continue to code energy at a 75 coderate to section 2-3T and relays ZTR and ZRCR will continue to operate ata 75 code rate and transmit a reverse code to section 2-3T of suchpolarity that rail 2 is energized positively and rail I is energizednegatively. Furthermore, signal 2S will continue to display its redaspect due to the fact that relay 2BR will remain released.

Therefore, at signal location A, relay 3D'I'R will continue to operateat a 75 code rate and relay 3HTR will remain released. Accordingly,relay 3DTFP will remain energized and relay 3HR will remain picked up.Therefor signal 3S will continue to display its green aspect.Furthermore, with relay 3HR remaining picked up, relay AACR willcontinue to transmit 90 code to section 4-5T in a manner alreadydescribed. Therefore, at location C, relay 5TB. will commence to operateat a 90 code rate and relays 5TFP and EHR will pick up. Therefore,signal 58 will now display a green aspect. Furthermore, with relay SHRnow picked up, relay 6CTP will commence to be energized at a code rateby a circuit which may be traced from positive terminal B of battery LB,over back contact I) of relay GI-I'IR, back contact b of relay BDTR,front contact a of coder ISBCT which is operating at a 180 code rate,front contact a of relay SHR, and the winding of relay ECTP to negativeterminal N of battery LB. Accordingly, relay liCI'P will commencetransmitting l8ocode to section 6*1T and, as long as the train occupiessection ES-l'T, this energy will be shunted by the wheels and axles ofthat train. The code assignments and signal aspects in my system when aneastbound train occupies section 6-11 are shown in Fig. 2c.

- However, when the eastbound train enters the eastern passing sidingand vacates section ii -1T, the 180 code being transmitted to section-6-1T will commence energizing relay 'ITR. Therefore, relays 'ITR and.TRCR will commence op' erating at a 1.80 code rate. Furthermore, relay'I DR. will now pick up and signal 1S will commence displaying a greenvaspect. Upon the picking up of relay 'lDR, the energizing circuit forrelay 8DP will become open at back contact b of relay FDR and relay 3DPwill release. Therefore, the reverse code being transmitted by relayTHC-R will. now be of such polarity that rail 1 will be energizedpositively and rail 2 energized negatively. It should be pointed out atthis time that, when the train enters eastern passing sidlng E, signal88 will indicate its stop or'red aspect and relay 8GP will release.Therefore, the energizing circuit for relay 8DP will be open at twopoints. With the reverse codebeing transmitted to section 6-TT of thepolarity described, relay fiH'l-R will commence operating and relayGD'IR will release. Therefore, relay EDTFP will release and relay BI-ITFP will pick up and establish a second energizing circuit for relaySHR, which has been previously described. Accordingly, signal 6S'will.display its yellow aspect due to energize.- tion of its yellow lamp Y bya circuit which may be traced from positive terminal B of battery LB,over front con-tact b of relay {Bl-IR, back contact b of relay EDTFP,and yellow lamp Y of signal 65 to negative terminal N of battery LB.Furthermore, with relay 6H5, now picked up, relay ACR and 53GB willcommence operating and thereby generate and transmit thirty-seven andonehalf. code to section 4-51. Accordingly, at signal location A, relayQTR will commence operating ata thirty-seven and one-half code rate andrelays lTFP and ll-IR will pick up. Therefore, relay 4ACR will commenceoperating as a reverse code transmitting relay, being energized at athirty-seven and one-half code rate by capacitor Q over previouslytraced circuits. Furthermore, with relay lHR picked up, signal is willnow display its green aspect.

With relay IZHR now picked up, energy will be supplied to relay 3CTP ata 180 code rate by a previously traced circuit. Therefore, relay 3CTPwill transmit normal 180 code to section 2-31 and, accordingly, relays2TB and ZRCR will commence operating at a 180 code rate. With relay 2THoperating at a 180 code rate, relay ZDR will pick up, thereby openingthe energizing circuit for relay I'DP at back contact I) of relay 2DR.Therefore, the reverse code being transmitted by relay ZRCR will be ofsuch polarity that rail I will be energized positively and rail 2negatively. Furthermore, with relay 2BR picked up, signal 28 will newdisplay its green aspect.

With the reverse code being, transmitted to section. 2-3T of thedescribed polarity, relay (ll-FIRv will commence operating and relay3DTR will release. Therefore, relay a'DTFP will release and relay BHTFPwill pick up and thereby establish another energizing circuit for relay3HR which has already been traced. Therefore, signal '38 will nowdisplay its yellow aspect due to the energization of the yellow lamp Yby a circuit including front contact 11 of relay til-IR and back contact'1) of relay 3DTFP.

From the above description, it should be clear that when an eastboundtrain occupies the east e'rnpassin'g'siding E, the system will berestored toits normal condition with the exception of signal 88 whichwill be displaying its red aspect as shown in Fig. 21. When the trainvacates' the eastern passing siding, signal 8S will clear up and thesystem. will be restored to its normal condition.

Having described an eastbound train movement, let it now be assumed thata train enters the stretch of track from the east and moves in awestbound direction. When the train is inthe eastern passing siding andapproaching the stretch of single track, signal 88 will display astop-aspect and relay 8GP will release. However; since relay 'lDR, ispicked up, there will be no efiect. upon the system and the system willcontinue to operate as it does in its normal unoccupied position, as'shown in Fig. 3?).

When. the westbound train occupies section 6-11, any energy beingsupplied to that track section will be shunted by the wheels and axlesof the train and, accordingly, the relays T'IJR, BDTR and SI-ITR willall be released. With relay 'ITR released, relay 'lRCR will release asno energy will be supplied to it over its previously traced energizingcircuit, and relay 'iDR will be released due to the fact thatinsufficient energy is being supplied to it through the decoding unit IDU. Accordingly, the previously traced circuit for energizing the greenlamp G of signal 1S will become open and the circuit for energizing thered lamp R. of signal 7%, which includes back contact a of relay 'IDR,will be closed. At signal location 0, with relays- EDTR and SI-ITRreleased, relays GDTFP, tI-lTFP and til-IR will all be released;Accordingly, the circuit for energizing the red lamp R of signal 6S,which includes back contact b of relay iii-IR, will become established.Furthermore, with relay GI-IR released, no energy will be supplied torelay 5ACR. Therefore, no energy will be supplied from track battery 5TBto track relay 4TB over the rails of section 4-51. Accordingly, relay5TB will release.

With relay 4TB. released, relays AIFP and ll-IR will. also release. Itwill be seen that with relay 4HR released and the remainder of thecircuit arrangement atlocation A in-the condition shown in Fig, 1a,relay lACR will commence operating at a 90 code rate in a, mannersubstantially identical to that already described. Accordingly, atsignal location C, track relay 5TB Will commence operating at a 90 coderate and relay BTFP' will remain picked up and continue to energizerelay SHE. Accordingly, acircuit including front contact b of relay 5BRwill remain established for energizing the green lamp G of signal Withrelay 4HR released, a circuit including back contact 0 of relay 4HR willbe established for energizing the red lamp R of signal 48. Furthermore,with relay EHR, picked up, relay 6CTP will be energized at a code rateby a circuit which has already been traced. Therefore, relay BCTP willcontinue to transmit 180 code to section B-IT. However, with a trainoccupying. the section, this 23 energy will be shunted by the wheels andaxles of the train.

Upon the release of relay IHR, a circuit for energizing relay 3C'IP at a'75 code rate which circuit has already been traced from positiveterminal B of battery LB, over front contact a of coder 150T, backcontact b of relay lHR, and the winding or relay 3CTP to negativeterminal N of battery LB will become established. Accordingly, relay3CIP will commence operating at a 75 code rate and thereby transmitenergy from battery 3TB to track relay 2TR over the rails of section2-3T. With relay 2TB, being energized at a 75 code rate, it will operateits contacts at a 75 code rate and accordingly supply energy to decodingunit ISDDU at a 75 code rate. Decoding unit I80DU will supplyinsufiicient energy to the relay ZDR, at a 75 code rate, to keep relay2BR picked up and, accordingly, relay ZDR will release. Therefore thecircuit for energizing the red lamp R at signal 28 will be establishedwhich circuit includes back contact a of relay 2BR. Upon the release ofrelay ZDR the circuit for energizing relay lDP will become establishedand thereby cause relay lDP to pick up and cause the reverse code beingtransmitted by relay :ZRCR to now be of such polarity that rail 2 willbe energized with energy of positive polarity and rail I will beenergized negatively. Accordingly, relay 3DTR will commence operatingand relay 3I-ITR will release. With relay 3DTR operating at a 75 coderate, relay SDTFP will pick up. With relay 3DTFP picked up, relay 3BRwill remain picked up as was previously described. Accordingly, acircuit will be established for energizing the green lamp G of signal38, which circuit has already been traced and which includes frontcontact b of relay SHR and front contact b of relay 3DTFP. Fig. 3c showsthe code assignments and signal aspects when a westbound train occupiessection B-TT.

When the westbound train vacates section 6-IT and occupies track section4-5T, any energy supplied to section 4-5T will be shunted by the wheelsand axles of the train and, accordingly, relay 4TB. will remain releasedand relay 5TB will release. With relay ETR released, relays 5TFP and 5HRwill release and signal 5S will display its red aspect. Furthermore,with relay 5HR released, the circuit for supplying energy at a '75 coderate to the winding of the relay SCTP will become established and relayGCTP will commence sup-plying 75 code energy to section B-lT.Accordingly, relay 'ITR will commence operating at a '75 code rate. Ashas already been explained, with relay lTR operating at a 75 code rate,relay IDR will remain released and thereby continue to energize the redlamp R at signal is. At this time signal 83 will be displaying a clearaspect and, accordingly, relay 8GP will remain picked up. Therefore, thecircuit for supplying energy to relay 3D? will remain established and itwill remain picked up. As was explained earlier, with relay ITRoperating, relay 'IRCR will operate and the two together will controlthe supply of energy from battery l'I'B to the rails I and 2 of sectionB-IT. With relay 8UP picked up the energy being supplied to section B-ITwill be of such polarity that rail 2 will be of positive polarity andthe rail l of negative polarity and, of course, the energy will be codedat a 75 code rate. Therefore, at location C, rela BDTR will commenceoperating at a 75 code rate and relay SI-ITR will remain released.Accordingly, relays BD'IFP and BI-IR will pick up. With re- 24 lays GHRand GDTFP picked up, signal 68 will display a green aspect due to theenergization of its green lamp G over a circuit including front contactb of relay BHR and front contact b of 5 relay BDTFP.

With relay BHR picked up, relays 5ACR and EBCR will commence operatingso as to generate and transit thirty-seven and one-half code to section4-5T. However, with a train in the section, this energy will be shuntedby the wheels and axles of the train. Therefore, as was previouslystated, relay ATR will remain released and relays ATFP and AHR will alsoremain released. With relay 4HR released, signal 48 will continuedisplaying its red aspect.

Furthermore, with relay lHR remaining released, relay 3CTP will continueto be energized at a 75 code rate and transmit '75 code to relay 2TB.Accordingly, relays ZTR and ZRCR will operate at a 75 code rate, relay-2DR will remain released and relay [DP energized. Therefore, signal 2Swill continue to display a red aspect and ZRCR will continue to transmita reverse 75 code of such polarity that rail 2 is energized positivelyand rail l negatively.

Therefore, at location A, relay 3DTR will continue to operate at a 75code rate and relay 3HTR will remain released. Accordingly, relays SDTFPand SI-IR will remain picked up and relay 3HTFP will remain deenergized.Therefore, signal 38 will continue displaying its green aspect.

With relay 3I-IR picked up, relay 4ACR will continue transmitting codeto section 4-5T. Of course, with the train now occupying that section,its wheels and axles will shunt the 90 code energy. However, asexplained with relation to an eastbound train movement, when the trainvacates section 4-5T, the thirty-seven and onehalf and 90 codes willscramble therefore assuring the system will reset for proper operationin a relatively short time.

The code assignments in the various sections and the aspects which theseveral signals will display with a westbound train in section 4-5'I' isshown in Fig. 311.

When the Westbound train vacates section l-5T and occupies section2-3'I', any energy supplied to section 2-3T will be shunted by thewheels and axles of the train and accordingly relays 2TB, 3DTR and3I-ITR will all be released. With relay 2TB now released, relay ZRCRwill also release and relay ZDR will remain released and, accordingly,signal 28 will continue to display a red aspect. With relay 2RCRreleased, no reverse code will be transmitted to section 2-31. Withrelays 3DTR and 3HTR released, relays 3DTW, and 3l-IR will release,relay 3HTFP will remain released, and signal 3S will display a redaspect. With relay 3HR released, no energy will be supplied to codetransmitting relay lACR and accordingly it will be released. Therefore,no code will be transmitted to section 4-5T from track battery 4TB overfront contact a of relay AACR. Therefore, relay 5TB will remainreleased.

With relay 5TB. released, no energy will be supplied to relay 'STFP orrelay SHR and these two relays will also remain released. With therelays at location C in this condition, relays EACR and 5BCR willcontinue to generate thirty-seven and one-half code in a manneridentical to that already described. Accordingly, at signal location A,relay 4TB will commence operating at a thirty-seven and one-half coderate, relay ATFP 25 will pick up and relay 4BR will also pick up.Therefore, signal 45 will display its green aspect. With relay TBreleased, relays 5TFP and BHR, will also be released and signal 55 willdisplay a red aspect. With relay ll-IR. now picked up, relay 3'CTP willcommence being energized at a 180 code rate by a previously tracedcircuit. Therefore, relay 3CTP will transmit 1 80 code to section 2-3T.However, with a train now occupying that section, the 180 coded energywill be shunted by the wheels and axles of the train.

Furthermore, with relay 5HR. released, the circuit for supplying energyto the winding of relay BCTP at a 75 code rate will remain establishedand, therefore, relay BCTP will continue to code energy from trackbattery 6TB to track relay 1TB at a code rate of 75. In a manner similarto that already described, with relays GUI? and 'ITR so oper ting, relay'IDR will remain released and thereby continue to energize the red lampof signal is. With relay 'IDR released the circuit for energizing relayBDP will remain established. With relay BDP picked up and relay 'ITRoperating at a 75 code rate, a reverse code at a 75 code rate ofpolarity such that rail 2 will be energized positively and rail lenergized negatively will continue to be transmitted by relay IRCR fromthe eastern headblock E to signal location C where this energy willcause relay BD'IR to continue operating and relay SHTR to remainreleased. Accordingly, relays SDTFP and BI-IR will remain picked up, andthereby maintain the energizing circuit for the green lamp G of signal(is. The code assignments for the various sections and the aspects whichthe several signals will display when a westbound train occupies section2-3T are shown in Fig. 36.

When the westbound train moves into the western passing siding W, the180 code which was being transmitted by relay 3CTP will now be receivedlby relay 2TB, which will commence operating its contacts at a 180 coderate. Accordingly, relay ZDR, will. pick up and energize the green lampG of signal 28. Furthermore. relay ZRCR will commence operating at a 180code rate. With relay ZDR picked up, relay IDP will release and thereverse 180 code .now being transmitted by relay ZRCR to signal locationA will be of such polarity that relay 3I-I'I'R. will commence operatingand. relays SDTR and SDTFP will release. Accordingly, relays 3H'IFP and3HR will pick up and energize the yellow lamp Y of signal 38 in a manneralready described. Furthermore, with relay 3BR picked up, the previouslytraced circuit for connecting capacitor Q across the winding of relay4ACR will be reestablished and relay 4ACR will commence transmitting areverse thirty-seven and one-half code to location C where athirty-seven and one-half code is being generated in the manner alreadydescribed. Accordingly, relay 5TB. will pick up and energize relays 5TFPand EHR. Therefore, signal 58 will display its green aspect.Furthermore. with relay 5HR picked up, a reviously traced circuit forenergizing relay GC'I'P 180 times per minute will be reestablished andrelay BCTP will transmit a 180 code to relay 1TB which will commenceoperating its contacts 180 times per minute. With relay (TR sooperating, relay IDR will pick up and signal is will display its clearaspect. With relay 'IDR picked up, relay BDP will release. Furthermore,with relay 1TB. operating its contacts 180 times per minute, relay 'IRCRwill commence operating its contact times per minute and with relay BDPreleased, will transmit a 180 reverse code of such polarity that relayGl-ITR will commence operating at a 180 code rate and relay fiI-IR willremain picked up. Accordingly, as already described, relay 5ACR willcontinue transmitting thirty-seven and one-half code to relay 4TB. Ascan be seen from the description, when the westbound train moves intothe western passing siding W, the system is restored to its normalcondition except that signal IS will display its stop aspect. The codeassignments and signal aspects of the system when a westbound trainoccupies the western passing siding is shown in Fig. 31. When thewestbound train moves out of the western passing siding, signal IS willclear up and the system will be restored to normal.

It will be clear that the additional conventional circuits, coded energyfor the control of cab signal equipment could be included in my novelsystem. Furthermore, by the addition of conven tional circuits at theheadblock locations, provision can be made for following moves in mynovel system.

It will also be clear that by polarizing the code being transmitted insection 4-5T, a third indication can be provided for signals 4S and 55.

Although I have herein shown and described only one form of apparatusembodying my invention, it is to be understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of single track railway extendingbetween two points, the rails of said track being divided by insulatedjoints into a first end section, an intermediate section and a secondend section, a first coder for generating code of one code rate at theend of said intermediate section adjacent said first end section, asecond coder for generating code of another code rate at the end of saidintermediate section adjacent said second end section, a code halvingmeans associated with each, coder, means for generating reverse code atthe first end of said intermediate section, code transmitting means ateach end of said intermediate section, means for connecting said secondcoder and its associated code halving means to their associated codetransmitting means except when said second end section is occupied,means for connecting said reverse code generating means to itsassociated code transmitting means when said stretch is vacant, meansfor connecting said first coder and its associated code halving means totheir associated code transmitting means when said intermediate sectionor said second end seciton is occupied, code following track relay meansat each end of said intermediate section operated by the energy suppliedover the rails from the opposite end of said intermediate section, and asignal at each end of said intermediate section controlled by itsassociated track relay means.

2. In combination, a stretch of single track railway extending between afirst and a second location, the rails of said stretch being divided byinsulated joints into a first end section adjacent said first location,a second end section adjacent said second location and an intermediatesection between said first and second end sections, track relay meansassociated. with said first and second end sections at the ends adjacentsaid first and second locations, respectively, reverse zCOde generatingmeans associated with said first and second end sections at the endsadjacent said first and second locations, respectively, means forreversing the relative polarity of the reverse code generated at the endof said end sections adjacent said first and second locations,respectively, when said stretch is vacant, track relay means selectivelyresponsive to energy of opposite polarity at the end of said first andsecond end sections remote from said first and second locations,respectively, a first and a second coder for generating codes atdifierent code rates located at the junction of said first end sectionand said intermediate section, a third and a fourth coder for generatingcodes at different code rates located at the junction of saidintermediate section and said second end section, means for generatingreverse code at the end of said intermediate section adjacent said firstend section, a code halving means associated with said second coder, acode halving means associated with said third coder, code transmittingmeans located at each end of each section, means for connecting saidsecond and fourth coders to their associated code transmitting means atthe end of said first and second end sections remote from said first andsecond locations when said stretch is vacant or their associated sectionis occupied, means for connecting said first and third coders to theirassociated code transmitting means at the end of said first and secondend sections remote from said first and second locations when either ofthe non-associated sections is occupied, said reverse code generatingmeans at the end of said first and second sections adjacent saidfirstand second locations, respectively, being continuously connected toits associated reverse code transmitting means, means for connectingsaid third coder and its associated code halving means to theirassociated code transmitting means except when said second end sectionis occupied, means for connecting said reverse code generating means atthe first end of said intermediate section when said stretch is vacant,means for connecting said second coder and its code halving means totheir associated code transmitting means when said second end section orsaid intermediate section is occupied, and a signal at each end of eachsection controlled by its associated track relay means.

3. In combination, a stretch of single track railway extending between afirst and a second location, the rails of said stretch being divided byinsulated joints into a first end section adjacent said first location,a second end section adjacent said second location and an intermediatesection between said first and second end sections, track relay meansassociated with said first and second end sections at the ends adjacentsaid first and second locations, respectively, reverse code generatingmeans associated with said first and second end sections at the endsadjacent said first and second locations, respectively, means forreversing the relative polarity of the reverse code generated at the endof said end section adjacent said first and second 10- cations when saidstretch is vacant, track relay means selectively responsive to energy ofopposite polarity at the end of said first and second end sectionsremote from said first and second locations, respectively, a first and asecond coder for generating codes at a first and a second code rate,respectively, located at the junction of said first end section and saidintermediate section, a third and a fourth coder for generating codes atsaid first and said second code rate, respectively, located at thejunction of said intermedifor generating reverse code at the end of saidintermediate section adjacent said first end section, a code halvingmeans associated with said second coder, a code halving means associatedate section and said second end section, means with saidthird coder,code transmitting means located at each end of each section, means forconnectingsaid second and fourth coders to their associated codetransmitting means at the end of said first and second endsections-remote from said first and second locations when said stretchis vacant or their associated section is occupied, means for connectingsaid first and third coders to their associated code transmitting meansat the end of said first and second end sections remote from said firstand second locations when the non-associated sections are occupied, saidreverse code generating means at the end of said first and second endsections adjacent said first and second locations, respectively, beingcontinuously connected to its associated code transmitting means, meansfor connecting said third coder and its associated code halving means totheir associated code transmitting means except when said second endsection is occupied, means for connecting said reverse code generatingmeans at the first end of said intermediate section when said stretch isvacant, means for connecting said second coder and its code halvingmeans to their associated code transmitting means when said second endsection or said intermediate section is occupied, and a signal at eachend of each section controlled by its asso ciated track relay means.

References Cited in the file of this patent UNITED STATES PATENTS Number

